China's manned deep-sea submersible Jiaolong aims to dive to a depth of 7,000 meters in the Mariana Trench on June 25 after already surpassing the record for the nation's deepest descent.

The Jiaolong reached depths of 6,671, 6,965 and 6,963 meters in its three dives from June 15 to 22, well surpassing the previous record of 5,188 meters last July.

Jiaolong, China's manned deep-sea submersible, finishes its second dive into the Mariana Trench on June 19, 2012. [Photo/Xinhua]

In the Jiaolong's third dive, which started at 7 am local time Friday (2100 GMT Thursday) and lasted about 10 hours, the vessel with a crew of three tried six bottom maneuvers and worked for more than three hours on the sea floor.

The crew also collected three samples each of water and sediment and took numerous photos of the trench's sea life.

Problems remain with the submirsible's adjustable ballast system, however, and must be corrected before the fourth dive, mission headquarters said.

The Xiangyanghong 09, the vessel's oceanographic mother ship, arrived at the designated dive zone in the western Pacific Ocean on June 11.